This proposal defines the development and evaluation of a dedicated microwave device for rapid, automated, and standardized fixation of tissue biopsies for histopathological examination. Microwave energy is used in combination with dilute aldehyde or salt solutions to produce fixation results that are equal in quality to chemical methods and equal in speed to freezing methods. Microwave fixation is in limited use by many pathology laboratories throughout the world. Household microwave ovens are the primary microwave device in use in the laboratory environment but have several performance (e.g., nonuniform irradiation) and safety (e.g., cannot adequately vent toxic chemicals) limitations. A rapid and automated microwave fixation device is important for patient care and research because it shortens the preparation time of a tissue specimen in the laboratory, improves technician safety and may improve the accuracy of diagnoses. We plan to 1) develop a single mode microwave device that uniformly irradiates biopsy tissue and controls final irradiation temperature noninvasively using a proven radiometer; and 2) evaluate the microscopic anatomy and staining quality with routine and special stains (e.g., Masson Trichrome, PAS, silver stains) of rat tissues (e.g., liver, brain, muscle, salivary gland) fixed by the prototype microwave device. PROPOSED COMMERCIAL APPLICATION: A reliable device for fast uniform fixation is needed now. Consolidation of regional hospitals and emphasis on improved efficiency are increasing the number of specimens handled by pathology departments. For example, a medium-size hospital, such as Beth Israel Hospital, processes over 25,000 specimens a year. An automated microwave fixation device offers the potential for decreasing the handling time of tissue biopsies and for improving the diagnostic quality of specimens.